Have been a/b-ing the Mikros 90 and the highly-touted KEF M500 for the last few weeks and in my mind there is no contest. The MLs retrieve a LOT more information than the KEFs, extend further in the treble and the bass frequencies, resolve much more thoroughly and trounce the M500 in virtually every other respect.

For classical, jazz, pop (I listened to Michael Jackson's landmark "Off the Wall" last night), world, show, chamber, acoustic, country and rock (from the 60s and 70s), the Mikros 90--in my ears--are among the best headphones I have ever heard/owned to date, and I have heard quite a few. They do require ample burn-in, 50-100 hours IMHO, need a little effort to optimize placement on the ear/head and benefit greatly from an after-market cable (I am currently using the Pipeline ET-4 to great advantage). The MLs scale up very well with better equipment. In my comparisons between the M500 and the Mikros 90, better equipment emphasized the comparative weaknesses of the KEFs but highlighted the comparative strengths of the MLs. (The KEFs are currently up for sale. The popular preference on H-F for the M500 over the Mikros 90 quite frankly baffles me.)

If you like detail, frequency extension, an airy presentation, transparency with full measure of musical transcendency, the Mikros 90 deliver in spades. Period. They also seal well and leak little--another area where the Mikros 90 easily bettered the M500.

I already ordered the used pioneer's, but I think I'm about to take a leap of faith and cancel the order to get the ML's instead.... I don't know enough of Pioneer's customer service and since they are used, I probably can't get warranty on them. Getting warranty on these and at a lower price seems like too good to pass up... I hope everything you have stated is true.

My one thought, the ML's have a very accurate and fast transducer, that does an incredible job of reproducing the signals fed it, I listen to virtually every type of music from death metal to classical organ and jazz, the better the recording the more rewarding the listen. Highly recommended for all types of music. If it has lots of bass, you will hear it, as the musician intended, not lots of extra distorted bass, just what is in the recording, these headphones own in bass reproduction, sub bass if your recordings have it, and many do, but few systems will reproduce what these gems will reveal.

I'm going to chip in here and say that you're probably better off with an HDJ200 than with the Mikros 90. Those Pioneers are some of the most underrated headphones currently on the market. I think you'll be very happy with them.

Haha so many different opinions and it just makes it harder for me to decide.

The pioneers will be my first pair of quality cans... What should I look for or expect when evaluating the sound?

It's not that the HDJ-2000s are a bad headphone, it's just that they are sorta like a one-trick pony when you compare them to the Mikros. The Pioneer will do something like hip-hop very well, but it will lag behind the Mikros with most other music genres.

I respectfully disagree about that. Of all of the headphones you can find in the general selection of a major store like Best Buy or an Apple Store, I think the HDJ2000 comes across as the most resolving and balanced there. It's warm, but not dull and muddy like a TMA-1 or removed and lifeless like a UE6000. It has just the right amount of sparkle for acoustic guitars to shine without getting overly in your face, and the bass hump is rather small compared to its competitors.

All of it's very subjective, so really it's all up to how you feel about them when you get them, Alex.

I respectfully disagree about that. Of all of the headphones you can find in the general selection of a major store like Best Buy or an Apple Store, I think the HDJ2000 comes across as the most resolving and balanced there. It's warm, but not dull and muddy like a TMA-1 or removed and lifeless like a UE6000. It has just the right amount of sparkle for acoustic guitars to shine without getting overly in your face, and the bass hump is rather small compared to its competitors.

All of it's very subjective, so really it's all up to how you feel about them when you get them, Alex.

Have you heard the Mikros?

I'm not saying that the HDJ2000 is bad...it's just that the Mikros 90 is better, IMO.

Have not heard the HDJ2000, personally, but I consider the Mikros 90 a truly REFERENCE class set of headphones. They do some things, IMHO, even better than my HifiMAN HE-6. To me, they handily beat the very popular KEF M500 across the board.

The MLs are extremely resolving, but they are ever musical and never clinical,

I think we all have a tendency to hyperbole...I'm as guilty as the next. Pulled out the HDJ2000 to do a quick comparison with the Mikros. I still think the Mikros is "better", more resolving, open, wider stage, fine detail. But you know what? I enjoyed listening to the Pioneer perfectly well. Bass is nice, treble now as clean but there, bass slightly stronger. Sounds more "hi-fi" to me, more realism in the Mikros, but it's all not the real thing (went out to hear jazz last night at a club, nothing comes close live music), and I enjoyed listening to the HDJ2000 just fine if I wasn't going back and forth and putting on my "reviewer" cap.

I think we all have a tendency to hyperbole...I'm as guilty as the next. Pulled out the HDJ2000 to do a quick comparison with the Mikros. I still think the Mikros is "better", more resolving, open, wider stage, fine detail. But you know what? I enjoyed listening to the Pioneer perfectly well. Bass is nice, treble now as clean but there, bass slightly stronger. Sounds more "hi-fi" to me, more realism in the Mikros, but it's all not the real thing (went out to hear jazz last night at a club, nothing comes close live music), and I enjoyed listening to the HDJ2000 just fine if I wasn't going back and forth and putting on my "reviewer" cap.

I think the word I was looking for earlier to describe what I felt about the HDJ2000 was that it's smooth. The treble has just a little sparkle, the bass has just a little emphasis, but none of it is accented to the point of harsness or boominess. That's why I like it so much. I like the Mikros more with certain music, but it has a few frequency peaks that keep it from being a true all-rounder for me. If I'm going to buy something for portable use, it's gotta be an all-rounder.